Table 4.

Relationship between serum prolactin levels and causes [68, 69]

Prolactin levels	Causes
< 100 ng/mL	• Stalk effect (increased prolactin due to impaired prolactin inhibitory factor delivery by compression to the pituitary stalk): nonfunctioning pituitary macroadenoma, Rathke’ cleft cyst, craniopharyngioma, germinoma, etc.
	• Drugs: Anti-ulcer drug, antiemetic drug, antihypertensive drug, psychotropic drug, oral contraceptives, etc.
	• Primary hypothyroidism
	• Pregnancy
	• Breast sucking stimulation
	• Prolactinoma
100–200 ng/mL	• Prolactinoma if drug-induced cause is excluded
> 200 ng/mL	• Macro-prolactinoma
> 1000 ng/mL	• Macro-prolactinoma with cavernous sinus invasion
	• Giant (> 4 cm) prolactinoma